1. Field of the Invention
The field of the invention is spark plugs for internal combustion engines.
Spark plugs are used to ignite a mixture of fuel and air within a combustion engine. Typically, a spark plug conducts a high voltage from a terminal connection to an electrode positioned within a combustion chamber. During the compression stroke of the piston, a spark is created between this electrode and a ground electrode to ignite the fuel-air mixture.
Conventional spark plugs that are used in fuel ignition systems, however, suffer from a number of limitations. For example, during the compression stroke, when the piston compresses the fuel-air mixture, a non-uniform distribution of fuel and air is created. This non-uniform distribution of fuel and air poses problems for combustion engines, including, for example, decreased efficiency and increased emissions of unburned fuel.
Generally, as the fuel-air mixture is compressed, the mixture of fuel and air near the spark plug electrode is richer, or thicker than the surrounding gases. When the electrode of the spark plug discharges, the region containing the thicker mixture of fuel and air is the first to ignite. The flame then travels outward, along the inner surface of the combustion chamber where the mixture is thinner, i.e., leaner. Finally, the flame spreads to the main area of the combustion chamber, where the mixture of fuel and air is leanest.
Unfortunately, this mixture of fuel and air in the main combustion chamber takes longer than desired to finish burning. Consequently, this often results in the discharge of unburned fuel and air. This problem is more acute when the engine operates at high rotation speeds where it is increasingly difficult to finish burning before the next cycle. The unburned fuel thus lowers the fuel efficiency of the entire system.
The expulsion of unburned fuel possess numerous problems as well. For example, the release of fuel into the atmosphere is known to deleteriously affect the environment. As a result, prior to release in the atmosphere, this unburned mixture is often passed through a separate and expensive catalytic converter device.
Attempts have been made at encapsulating electrodes to improve ignition. However, these designs have also had numerous shortcomings such as large heat losses in the ignition period as well as problems associated with long term usage, i.e., oil burning and carbon deposition on the electrode. Moreover, these devices have altered compression ratios and prevented the self-cleaning of spark plug electrodes.